1. Field of the Invention
This present invention relates to the field of relatively compact scanner apparatus and methods and more particularly to apparatus and methods for scanning objects which are transported by a conveyor belt through a temporarily sealed tunnel, such as in contraband detection systems.
2. Description of the Prior Art
Scanners, particularly "compact" scanners, are used for detecting contraband at schools, correctional mail screening, courthouse security, airport hand parcels, and industrial processing applications. These scanners employ tunnel housing, usually leaded and wired in part on the outside, an isolating device, a conveyor device, a bed assembly housing in which the conveyor device is substantially located, and framing and thinner painted covers to hide the unsightly framing and the lead. The tunnel housing typically has a top portion, and side portions which together with a top portion from the bed assembly housing, form a substantially enclosed area. The tunnel housing is also provided with entrance and exit openings to the substantially enclosed area.
The isolating device substantially covers the entrance and exit openings and is typically in the form of two separate lead curtains. One lead preferably fabric curtain is bolted to flat framing at the entrance opening, and the other lead preferably fabric curtain is bolted to flat framing located at the exit opening. Isolating devices permit the passage of conveyed objects into the substantially enclosed area formed by the tunnel housing and the top portion of the bed assembly housing, which is typically x-ray scatter lead shielded on the outside and may also substantially exclude light, noise, heat, cold, moisture, dryness, electrostatic or electromagnetic fields, dust gasses or chemical vapors while the conveyed objects are being analyzed.
Scanners analyze objects which are brought into the enclosed area formed by the tunnel housing and the top portion of the bed assembly housing by the conveyor device. The conveyor devices are typically comprised of relatively short lengthened conveyor belts. Short lengthened conveyor belts, particularly those with a relatively low length to width ratio, such as of less than twelve to one, 12 to 1, often mistrack causing damage to the conveyor belts, objects being scanned, and other parts of the system. Currently, expensive and elaborate tracking mechanisms such as precise construction of components, toothed or perforated belting to mesh with drive gears or belt grooves raised, profile rails, servo-drive tracking adjustment mechanisms, and reliance on a human attendant are used for tracking conveyor belts.
The framing provided to structurally connect the tunnel housing, the bed assembly housing, the conveyor device and the isolating device is often elaborate, wasteful, and space consuming, and requires a plurality of cover panels to hide the framing, the lead, the detector assembly and wiring. Scanners are needed which are more compact in overall width and length without sacrificing the width of the enclosed area inside the tunnel housing, and which are simpler and less costly to manufacture.